Embryology of the Urogenital Systems

Question 1

What type of embryonic tissue does the urinary (and genital) system develop from?

Answer 1

Intermediate mesoderm of trilaminar disc.

Question 2

What does intermediate mesoderm separate from?

Answer 2

From lateral and paraxial mesoderm during folding and forms urogenital ridge.

Question 3

What forms the urogenital ridge?

Answer 3

Intermediate mesoderm separates from lateral and paraxial mesoderm during folding and forms urogenital ridge.

Question 4

At what week of development is the mesonephros present and functional?

Answer 4

weeks 6 -10

Question 5

After week 10 of development, the mesonephros degenerates except for?

Answer 5

> the duct system will contribute to part of the male genital system (ductus deferens).

> some vestigial structures in the female.

Question 6

Even though the metanephros is not functional in women, what is it still important?

Answer 6

Because it contributes to the development of the ureter.

Question 7

True or False:

Renogenesis involves a process of reciprocal induction, which is not retinoic acid dependent.

Answer 7

False - renogenesis involves a process of reciprocal induction, which IS retinoic acid dependent.

Question 8

What establishes a renogenic region within the intermediate mesoderm in the tail of the embryo?

Answer 8

Cranial-caudal patterning

Question 9

What is the metanephric blastema?

Answer 9

renogenic mesoderm is the METANEPHRIC BLASTEMA

Question 10

What does the metanephric blastema secrete?

Answer 10

Secretes growth factors that induce growth of the URETERIC BUD from the caudal portion of the mesonephric duct.

Question 11

What induces growth of the ureteric bud from the caudal portion of the mesonephric duct?

Answer 11

the metanephric blastema secretes growth factors that induce growth

Question 12

True or False:
The ureteric bud proliferates and responds by secreting growth factors that stimulates proliferation and then differentiation of the metanephric blastema into glomeruli and kidney tubules.

Answer 12

True

Question 13

What differentiates into glomeruli and kidney tubules?

Answer 13

metanephric blastema

Question 14

What can cause inhibition of ureteric bud growth and renal hypoplasia or agenesis?

Answer 14

perturbations in any aspect of these inductive events (e.g., mutations of either metanephric or ureteric factors or disruption of retinoic acid signaling

Question 15

At which week of development does blood plasma from glomerular capillaries begins to be filtered?

Answer 15

10th week

Question 16

Urine is produced by the 10th week of development, but what is the primary function of the urine?

Answer 16

Primary function is not to clear waste (placenta) but to supplement production of amniotic fluid.

Question 17

What may oligohydramnios (insufficient amount of amniotic fluid indicate?

Answer 17

May indicate bilateral renal agenesis or urethral obstruction.

Question 18

What is oligohydramnios?

Answer 18

insufficient amount of amniotic fluid

Question 19

What is the in utero function of the metanephros?

Answer 19

To filter blood plasma from glomerular capillaries at the 10th week of development, which produces urine. This urine is supplemental production of amniotic fluid.

Question 20

List the clinical considerations that we are responsible for in this lecture.

Answer 20

• accessory renal vessels
• renal agenesis
• renal ectopia
• renal fusion
• urachal fistula or cyst
• Wilms tumor

Question 21

In what percentage of individuals do accessory renal vessels occur and from where do they arise?

Answer 21

10% of individuals and 98% arise from the abdominal aorta.

Most enter the renal pelvis and pose little problem

Question 22

Where can aberrant renal arteries enter the kidney that pose problems?

Answer 22

Upper or lower poles of the kidney.

Question 23

Aberrant arteries to the inferior pole of the kidney (4-6%) may be caused by what?

Answer 23

Obstruction of the ureter and may cause an intermittent or continuous obstruction to urinary drainage from the renal pelvis.

Question 24

True or False:

Aberrant renal vessels enter the kidney independently from the primary renal vessels.

Answer 24

True

Question 25

You know that kidneys are formed in the pelvis and ascend to the lumbar region, but with progressive revascularization from what?

Answer 25

Common iliac and aorta.

Question 26

Where are kidneys formed and where do they ascend to?

Answer 26

Kidneys are formed in the pelvis but ascend to lumbar region with progressive revascularization from common iliac and aorta.

Question 27

What two things cause Potter's syndrome (pulmonary hypoplasia)?

Answer 27

- Oligohydramnios | - Fetal compression

Question 28

What causes amnion nodosum?

Answer 28

Oligohydramnios

Question 29

Is Potter's syndrome diagnosed in utero?

Answer 29

Yes

Question 30

What does renal fusion prevent in normal kidney development?

Answer 30

Normal rotation of kidney.

Question 31

In patients with renal fusion, from what arteries is typical abnormal blood supply coming from?

Answer 31

Usually from middle sacral or common iliac arteries.

Question 32

What is the typical shape (defining structure) of a kidney in a patient with renal fusion?

Answer 32

Horseshoe kidney

Question 33

What percentage of horseshoe kidneys are fused at the lower pole?

Answer 33

90%

Question 34

What landmark is horseshoe kidneys typically found inferior to?

Answer 34

Inferior mesenteric artery. **because the horseshoe kidney gets stuck under the inferior mesenteric artery when the kidney is ascending during development**

Question 35

What is Wilms' tumor and who is usually affected?

Answer 35

Cancer of the kidney and usually affects children under the age of 5.

Question 36

A mutation in what gene causes a Wilms' tumor?

Answer 36

Mutations in the WT1 gene.

Question 37

Give the diagnosis: A 3 month-old previously healthy boy presented with hematuria. A renal ultrasound, and subsequent chest, abdomen, and pelvis CT exam demonstrated a large heterogeneous right renal mass.

Answer 37

Wilms' Tumor

Question 38

Once the cloaca is divided by the urorectal septum, what does the dorsal (inferior) portion develop into?

Answer 38

Rectum and Anal Canal

Question 39

Once the cloaca is divided by the urorectal septum, what does the ventral (superior) portion develop into?

Answer 39

Bladder and Urogenital Sinus **which will give rise to the bladder and lower urogenital tracts (prostatic and penile urethrae in males; urethra and lower vagina in females)**

Question 40

What does the bladder and urogenital sinus give rise to?

Answer 40

Bladder and lower urogenital tracts (prostatic and penile urethrae in males; urethra and lower vagina in females).

Question 41

What develops into the bladder and urogenital sinus?

Answer 41

The ventral (superior) portion of the cloaca once it has been divided by the urorectal septum.

Question 42

What develops into the rectum and anal canal?

Answer 42

The dorsal (inferior) portion of the cloaca once it has been divided by the urorectal septum.

Question 43

What gives rise to the bladder and lower urogenital tracts (prostatic and penile urethrae in males; urethra and lower vagina in females)?

Answer 43

Bladder and Urogenital Sinus.

Question 44

Before the cloaca is divided, what is it?

Answer 44

A common outflow tract for GI and bladder.

Question 45

Between what weeks in development does the mesonephric duct and ureteric bud incorporate into the posterior wall of the urinary bladder?

Answer 45

4-6 weeks

Question 46

What are the difference between the openings of the ureteric buds and mesonephric ducts?

Answer 46

>Ureteric buds - open into bladder wall >Mesonephric ducts - open more inferiorly into the pelvic urethra **ductus deferens doesn't open into the bladder**

Question 47

What forms the trigone of the urinary bladder?

Answer 47

The triangular region of the incorporated mesonephric duct incorporated in the bladder wall forms the trigone.

Question 48

Why do you want the ductus deferens inferior to the bladder?

Answer 48

So the bladder can get larger and to make sure that semen and urine are not mixing.

Question 49

What is a urachal fistula or cyst?

Answer 49

> Bladder is continuous superiorly with allantois (which should collapse and become the urachus). > The urachus may remain patent throughout its length (urachal fistula) or only at an end (urachal sinus). > Remnants of the urachal lumen may also give rise to urachal cysts. These usually present as an abdominal mass.

Question 50

What is a way to diagnose a urachal fistula or cyst?

Answer 50

If urine is coming out of the umbilical cord.

Question 51

True of False: The genotype of the embryo is established at fertilization.

Answer 51

True

Question 52

What state does the embryo remain in during weeks 1-6?

Answer 52

Remains in a undifferentiated state.

Question 53

At what week of gestation does phenotypic sexual differentiation begin?

Answer 53

Week 7

Question 54

At what week of gestation can the male and female external genitalia be recognized?

Answer 54

Week 12

Question 55

At what week of gestation is phenotypic differentiation complete?

Answer 55

Week 20

Question 56

What does the Wolffian (mesonephric) duct develop into?

Answer 56

- epididymis - vas deferens - seminal vesicle - ejaculatory duct

Question 57

What does the Mullerian (paramesonephric) duct develop into?

Answer 57

- fallopian tubes - uterus - upper part of vagina

Question 58

Where is the SRY encoded on the Y-chromosome?

Answer 58

On the sex-determining region.

Question 59

What does the synthesis of SRY protein (testis-determining factor, TDF) trigger?

Answer 59

Male Development

Question 60

What happens if SRY protein is not synthesized?

Answer 60

Female path is followed.

Question 61

Which sex is the basic (default) developmental pathway?

Answer 61

Female

Question 62

True of False: | In the development of genital ducts, two pairs of ducts are present in both sexes.

Answer 62

True

Question 63

True of False: | Both pairs of ducts are present during the indifferent stage (weeks 1-6).

Answer 63

True

Question 64

Which ducts play the most important role in the male?

Answer 64

mesonephric ducts

Question 65

Which ducts play the most important role in the female?

Answer 65

paramesonephric ducts

Question 66

What are the 4 stages of sex determination in mammals?

Answer 66

1) genetic sex 2) gonadal sex 3) phenotypic sex (internal and external) 4) behavioral and metabolic sex

Question 67

Which 3 tissues do gonads develop from?

Answer 67

- epithelium of intraembryonic coelom - intermediate mesoderm - primordial germ cells

Question 68

During the development of gonads, what does the primordial germ cells from the mesoderm of the yolk sac invade?

Answer 68

The dorsal mesentery and migrate to urogenital ridges.

Question 69

Primary sex cords are aggregates of what?

Answer 69

Supporting cells (hormone secreting cells).

Question 70

What is a phallus?

Answer 70

clitoris or penis

Question 71

What are (uro)genital folds?

Answer 71

labis minora or shaft of the penis

Question 72

What are labioscrotal (genital) swellings?

Answer 72

labis majora or scrotum

Question 73

List 6 paramesonephric duct anomalies.

Answer 73

``` > uterus didelphys with double vagina > uterus arcuatus > uterus bicornis > uterus bicornis unicollis and 1 rudimentary horn > atresia of cervix > atresia of vagina ```

Question 74

What can cause cervical or vaginal atresia?

Answer 74

Partial or total atresia of the distal portion of both ducts.

Question 75

True of False: 46, XY can have persistence of paramesonephric ducts if the circulating levels of AMH are low or there is an abnormal response to normal AMH.

Answer 75

True

Question 76

What is Mullerian agenesis caused by?

Answer 76

Failure of the paramesonephric ducts to develop.

Question 77

What does Mullerian agenesis result in?

Answer 77

Missing uterine tubes, uterus, and variable malformations of the upper portion of the vagina.

Question 78

What is Mullerian agenesis also known as?

Answer 78

MRKH or Mayer-Rokitansky-Kuster-Hauser Syndrome

Question 79

What is hypospadias caused by?

Answer 79

Incomplete fusion of the urethral folds.

Question 80

What does incomplete fusion of the urethral folds cause?

Answer 80

hypospadias

Question 81

What does hypospadias do to external genitalia?

Answer 81

Causes urethra to open onto the ventral aspect of the penis.

Question 82

What can hypospadias result from? Hint: what causes incomplete fusion of the urethral folds?

Answer 82

Can result from inadequate androgen production or inadequate receptor sites for DHT.

Question 83

What are the 4 types of hypospadias?

Answer 83

- glandular - penile - penoscrotal - perineal

Question 84

What are the characteristics of classic virilizing adrenal hyperplasia?

Answer 84

> female intersex > females (46, XX) with severe forms of adrenal hyperplasia have ambiguous genitalia at birth due to excess adrenal androgen production in utero. > Ambiguous genitalia ranges from complete fusion of the labioscrotal folds and a phallic urethra to only clitoromegaly, partial fusion of the labioscrotal folds, or both. > NO abnormalities of ovaries.

Question 85

What does increased exposure to androgens result in?

Answer 85

- clitoral hypertrophy | - labioscrotal fusion

Question 86

What is androgen insensitivity syndrome (AIS) - complete?

Answer 86

> An X-linked disorder in which receptors remain unresponsive to androgens. > Despite normal levels of testosterone, the male foetus fails to masculinise. > The external genitalia are feminine. Internally they possess non-functioning undescended testes. > At puberty, secondary female sexual characteristics may appear due to estradiol from testosterone aromatization. > It is common to perform gonadectomies at puberty and for them to receive hormone therapy, to be reared as female.

Question 87

What does the degree of feminization depend on in patients with male (46, XY) with testes and feminized genitals?

Answer 87

Affected androgens and the amount of residual receptor function.

Question 88

What is 5-alpha reductase deficiency (5-ARD)?

Answer 88

Autosomal recessive condition resulting in the inability to convert testosterone to the more physiologically active dihydrotestosterone (DHT).

Question 89

What is 5-ARD often misdiagnosed as?

Answer 89

AIS

Question 90

True of False: Because DHT is required for the normal masculinization of the external genitalia in utero, genetic males with 5-ARD are born with ambiguous genitalia (underdevelopment of penis and scrotum or pseudovaginal perineoscrotal hypospadias).

Answer 90

True

Question 91

Look at the course of development if SRY is expressed or not expressed.

Answer 91

Either male or female.